The present invention relates to low power electronic tags and tag tracking systems. More particularly, the present invention relates to radiofrequency tags externally triggered by a directed light or electromagnetic pulse.
Tagging objects to aid in identification, security, and organization is widely employed by businesses. Passive tag systems include conventional bar code tags, microwave detectable tags, or tags marked with computer readable alphanumerics. However, all of these tagging solutions generally require close proximity between the tag and the tag reader, typically less than a meter. For applications where tags need to be identified in a 1 to 5 meter range, active tags that have onboard power to broadcast radio or infrared pulses can be used. For example, a battery powered infrared tag utilizing IrDA pulse modulation can be constructed to emit an identification pulse sequence every 10 to 15 seconds, and can have a lifetime on the order of a year. However, since such active devices are costly, generally have a high power cost, and can require expensive battery or photovoltaic power systems, they are unsuitable for applications requiring hundreds or even thousands of tags.
Conventional passive (e.g. optically readable bar codes) or active (e.g. infrared emissive) tags can also be difficult to find or determine exact position in a room sized area. Imaging detectors such as camera systems are costly, and can require substantial computing power to extract data signals from a tag and determine three-dimensional position of the tag. What is needed is a tagging system that can be easily read from a distance with augmented portable computing devices such as handheld or palm-sized computers, or automatically determined (without user assistance) using a non-imaging room scanning system. Such tagging systems can support local communication between nearby computers, or more generally can support wireless network or internetwork communications relating to data signals from the tags. Users equipped with suitable portable computers can, for example, receive identifying information from local tags, and be connected to an updateable networked database that stores position state, identifying information concerning the tagged object, and a record of previous state changes for the tag. As will be appreciated, flexibility and utility of various applications can be enhanced if the precise spatial location of the tagged objects known. Knowing the location of the tag (with a precision of several meters or so) permits construction of user specific maps, transfer of location information to others, and receipt of location information for nearby computational or real world resources. For this reason, having easily determinable and reliable position information is a useful feature.
Improved information dissemination and organization for individuals or organizations is enhanced with a stable and reliable mechanism for tracking and locating multiple tagged objects in conventional room or office sized areas. Tagged objects can be assembled, manipulated, and maintained to create, alter, preserve, share, or coordinate information. For example, wall mounted pin boards or magnetic boards can be used by an individual or group to transiently or semi-permanently display documents, calendars, task schedules, phone number lists, project proposals, informational flyers, meeting announcements, photographs, maps, or any other desired information. In some cases, small physical artifacts such as keys or magnetic icons can even be attached to the surface.
Accordingly, in preferred embodiments the present invention includes a laser locating and tracking system for externally activated electronic tags. Such a non-imaging system can precisely locate and identifying tagged objects in a confined space such as a room or office. The system includes at least one laser base station for scanning laser beams, and supports identification and spatial positioning of multiple tags reactive to incident laser beams to provide a data signal. A tag tracking system receives input from the laser base station, with the tag tracking system storing state records of position and informational content of the tag. Position can be optionally determined by angular position of the tag with respect to one or more the laser base stations. The tags are passive (with no internal power), or active, having an internal power supply to power a data broadcast element.
An externally light activated, low power active electronic tag is particular useful in conjunction with the present invention. Such low power electronic tags and tag tracking systems can use infrared or radiofrequency tags having identification circuits externally triggered by a directed light pulse. Such tags generally have an internal power supply (e.g. battery), a data broadcast element controlled by a microcontroller and powered by the internal power supply, and a laser beam trigger circuit activated by an incident laser beam to trigger data broadcast by the data broadcast element. The data broadcast can be optical, infrared, radio, or even acoustic signals. A preferred data broadcast standard is based on the connectionless IrDA protocol pulse modulated infrared data signals. Such signals can be detected by conventional infrared transceivers commonly deployed with portable, laptop, or palmtop computers. The tags can be readily activated by a low power laser attached to a palmtop computer, for example, allowing a user to specify tag activation from a distance. Alternatively, automatic laser scanning systems can be used to continuously and automatically track tag positions.
For some applications the foregoing externally activated tags are not ideal, since they still require a battery, have a relatively large form factor, and can be somewhat expensive. For applications requiring very large numbers of identification tags, a bar code-like system readable from a distance (1 to 5 meters) is preferred. Accordingly, another preferred embodiment of the present invention provides for patterned retroreflective tags usable in laser scanning systems. Typically, such patterned retroreflective tags are multilayered, and the tags can have fixed or dynamically changeable laser readable regions. Typically, a tag identification system would include a tag having retroreflective substrate for reflecting incident light beams, and patterned indicia for selectively reducing retroreflectivity of the retroreflective substrate. A portable (handheld) or fixed laser beam base station connected to a computer can read the tag and associate the read tag with information, including data or commands for computer control.
In preferred embodiments, the patterned indicia of the tag are formed by selectively destroying portions of the retroreflective substrate. Alternatively, the patterned indicia are formed by selectively obscuring portions of the retroreflective substrate through surface printing, coating, or other suitable techniques. In multilayer embodiments, a printable and substantially transparent masking layer covering the retroreflective substrate can be used for printing. In still other embodiments that add some active elements to the passive tag, an electrically modifiable region (e.g. LCD, electrochromic material, or other conventional low power, electrically opaqueable material) can be used to selectively obscure portions of the retroreflective substrate. Typically, the opaqued or obscured regions are patterned as a series of stripe emulating conventional bar codes, although other coding patterns can of course be used.
Still another preferred embodiment of the present invention using the foregoing passive, active, or combination active/passive tags provides for a virtual control system using non-imaging scanners (e.g. laser scanning systems) by tracking relationships between light reflective or emissive tags. Advantageously, such a non-imaging system can identify virtual controls based on interrelationships between light reflective or to emissive tag positions. Typically, a user operated virtual control system involves scanning laser beams throughout a room using a laser base station and detecting data signals produced by multiple tags reactive to incident laser beams scanned throughout a room. By tracking positional changes of multiple tags, the positional semantics of the tag can be recognized and allow provision of a control signal in response to user defined location changes in at least one of the multiple tags. Positional changes in tag position can be relatively determined (e.g. with one laser base station) or absolute three dimensional position changes can be determined (e.g. with two or more laser base station, or other position detecting mechanisms such an antenna grid array responsive to radio signals. In a most preferred embodiment, passive retroreflectors are employed.
In certain embodiments of the present invention, electromagnetic induction activated electronic tags can be used for tag activation or location. Such radiofrequency tags are externally triggered by a directed electromagnetic pulse (e.g. from a microradar or narrow beam microwave source) or optical pulse (laser or infrared), and spatial tracking can involve separate electromagnetic tracking systems or laser scanning systems such as previously discussed.
One preferred embodiment of an electromagnetic tracking system suitable for use in conjunction with electronic tags has an embeddable antenna array for activation and localization of electronic tags. These tags can optionally be externally triggered by a directed electromagnetic pulse delivered through the antenna grid array, or triggered by an external light or electromagnetic source, with spatial location being determined with the aid of the antenna grid array.